1. Field of the Invention
The present invention relates to a cleaning method, a cleaning apparatus and an electro optical device.
2. Related Art
In a low molecular weight organic electro luminescence (EL) device, light emitting layers composed of low molecular weight organic materials are formed on a glass substrate. The light emitting layers composed of low molecular weight organic materials are formed by vapor-deposition. Vapor-deposition is a method in which a small piece of a material is heated and evaporated in a high vacuum so as to, be deposited on a substrate as a thin film. When light emitting layers are formed by vapor-deposition, a vapor-deposition mask needs to be disposed in order to prevent organic materials from attaching to regions other than the regions on which the light emitting layers are desired to be formed. In addition, protection plates need to be disposed in order to prevent organic materials from attaching to an inner wall and so forth of a vapor-deposition chamber.
Here, multiple vapor-deposition treatments results in a state in which organic substances are deposited on the surfaces of a protection plate, a vapor-deposition mask and so forth, which are manufacturing devices for organic EL devices. If a protection plate on which organic substances are deposited is permitted to repeatedly remain standing, the inside of a vapor-deposition chamber is contaminated. Also, the vapor-deposition mask that is formed of a metal thin plate or the like bends greatly because of the weight of the organic substances, thereby affecting the accuracy of patterning. Therefore, it is essential to remove the organic substances deposited on the protection plate, vapor-deposition mask and so forth periodically.
Thus, manual scrubbing away of organic substances deposited on a protection plate, a vapor-deposition mask and so forth is carried out by human hands. Also, in Japanese Unexamined Patent Publication No. 8-319586, a method in which a mixed gas plasma is generated in a treatment chamber after etching treatment so as to remove residual reaction products in the treatment chamber has been proposed. Furthermore, in Japanese Unexamined Patent Publication No. 2000-282219, a method in which organic films attached to a mask through organic-film vacuum deposition are removed by heat treatment without breaking a vacuum has been proposed.
The method of manual scrubbing (by human hands), however, suffers from a problem in that many workers are required. Thus, the establishment of a cleaning process that needs no human hands and is favorable in terms of working efficiency has been desired.
In both methods proposed in the above patent documents, organic films and so forth are removed in a treatment chamber (chamber), and therefore the modification of a vapor-deposition apparatus is required. Accordingly, there is a problem in that a large cost is required.
The present invention is devised in order to solve the above problems and is intended to provide a cleaning method and a cleaning apparatus that can easily remove organic substances attached to a manufacturing device for electro optical devices. Also, the present invention is intended to provide a high quality electro optical device.